In recent years, increased recognition of the many benefits of cardiovascular and aerobic exercise and body conditioning, in combination with continually increasing time constraints of modern lifestyles, have resulted in a large demand for exercise devices which can provide maximum benefits of exercise with a minimum of inconvenience and minimum time requirement. This demand has resulted in the development of numerous types of exercise machines and systems.
Exercise machines and systems may be categorized based upon the method and medium utilized to provide a resistive force against which the muscles are worked and the configuration of the structural elements of the apparatus through which the user athlete interfaces with the resistive medium. Prior to the advent of modern exercise machines and universal gyms, iron weights lifted against gravity were the most common resistance medium. Iron bars, used in combination with the weights as bar bells or dumb bells, were the apparatus which allowed the athlete to work his muscles in an appropriate manner against appropriate weight for selected enhancement of muscle development. Auxiliary apparatus, such as benches and weight racks, assisted in the positioning of the athlete's body relative to the orientation of gravity as appropriate. Such "free weight" exercise apparatus has many disadvantages. There is an ever present danger associated with the use of this equipment that a user athlete will loose control of the weight due to fatigue of the athlete's muscles or an attempt to lift more weight than the athlete's muscles are capable of controlling. Much time is required for changing weights and moving weights and auxiliary equipment to prepare for different exercises. Equipment for an extensive and thorough fitness program constitutes a great number of separate parts, i.e. weights, bars and auxiliary equipment, to be organized and stored.
Many contemporary exercise and universal gym devices continue to use iron weights, or weights made of other suitably dense material, to provide resistance for muscle exercise while attempting to overcome the dangers and inconvenience of free weight exercise apparatus. These devices confine the weights to movement along fixed tracks to eliminate dangers associated with loss of control and dropping of free weights during attempts to work the muscles against too great a force. The weights of these apparatus are connected by chains, levers and the like, in various configurations, to exercise members which are engaged and worked in a cyclical fashion during muscle conditioning exercises by the user athlete. These machines, however, also suffer from a number of disadvantages. First, they must be massive to provide the weight necessary for training advanced athletes and to provide the structural strength necessary to support and control that weight. Also, they are complex because all exercising motions must be translated into up and down movement of the weights along their tracks in the gravitational field. This latter consideration generally precludes the provision of an exhaustive selection of conditioning exercises by one such machine and necessitates the use of multiple machines for a complete fitness program.
Efforts to reduce the great mass associated with weight resistance devices and to free the design of exercise machine and universal gym structures from the constraints of orienting the movement of the resistance medium to an alignment with gravity, have lead to the development of a number of exercise devices based upon hydraulic resistance. While machines of this type differ in their hydraulic system design and their structural configuration for providing the interface between the user athlete and the hydraulic resistance system, the hydraulic systems of all these apparatus generally have two key elements in common; a hydraulic cylinder with a piston linked to an exercise member and arranged to pump fluid in and out of the cylinder in response to movement of the exercise member through an exercise cycle, and a static and/or dynamic flow resistance means for creating a resistive pressure in the cylinder against which the muscles are worked. Despite the large number of such machines known in the art, all are deficient in one or more respects.
Most hydraulic exercise apparatus heretofore known in the art utilize double-action hydraulic cylinders. The utilization of double-action hydraulic cylinders in many of these devices results in multi-directional resistance. That is, unlike exercise with free weights, exercising forces are provided by double-action cylinder devices which resist movement of the exercise member during both an exercise stroke and a return stroke of an exercise cycle. Due to this "two-way resistance", these devices fail to provide the benefits of muscle exercise which may be obtained with "free weight" exercising apparatus which do not provide a resisting force during the return stroke. Double-action cylinders are more complex and costly than single-action hydraulic cylinders, and are generally weaker than single action hydraulic cylinders of similar cost and size. Thus, in devices using double-action cylinders, the cylinders must be located further from fulcrum points requiring larger structures than can be provided by exercise devices utilizing single-action cylinders.
Many hydraulic exercise devices of the present art also lack sufficient configuration adaptability to provide a full range of individual muscle toning exercises necessary for true muscle conditioning program versatility. Further, few of these devices have structures which can fold into a compact configuration for ease of storage and transport. Adjustment of the level of exercising resistance provided by these devices is often cumbersome and, generally, the resistances can not be directly set in pounds. None of these devices provide for controlled variation of hydraulic resistance over the exercise stroke to provide for optimum exercise benefit. Many of these machines utilize designs requiring the use of multiple hydraulic cylinders in order to allow a reasonable number of different exercises to be accomplished with the aid of only that single machine, further increasing its mass and complexity. None of the hydraulic resistance exercise machines and universal gyms of the prior art have achieved great versatility of exercise configuration in combination with a structure sufficiently light and simple to allow those exercise machines and universal gyms to be readily and conveniently transported between different locations.